Plato (Platon, "the broad shouldered") was born at Athens in 428 or 427 B.C. He came of an aristocratic and wealthy family, although some writers represented him as having felt the stress of poverty. Doubtless he profited by the educational facilities afforded young men of his class at Athens. When about twenty years old he met Socrates, and the intercourse, which lasted eight or ten years, between master and pupil was the decisive influence in Plato's philosophical career. Before meeting Socrates he had, very likely, developed an interest in the earlier philosophers, and in schemes for the betterment of political conditions at Athens. At an early age he devoted himself to poetry. All these interests, however, were absorbed in the pursuit of wisdom to which, under the guidance of Socrates, he ardently devoted himself. After the death of Socrates he joined a group of the Socratic disciples gathered at Megara under the leadership of Euclid. Later he travelled in Egypt, Magna Graecia, and Sicily. His profit from these journeys has been exaggerated by some biographers. There can, however, be no doubt that in Italy he studied the doctrines of the Pythagoreans. His three journeys to Sicily were, apparently, to influence the older and younger Dionysius in favor of his ideal system of government. But in this he failed, incurring the enmity of the two rulers, was cast into prison, and sold as a slave. Ransomed by a friend, he returned to his school of philosophy at Athens. This differed from the Socratic School in many respects. It had a definite location in the groves near the gymnasium of Academus, its tone was more refined, more attention was given to literary form, and there was less indulgence in the odd, and even vulgar method of illustration which characterized the Socratic manner of exposition. After his return from his third journey to Sicily, he devoted himself unremittingly to writing and teaching until his eightieth year, when, as Cicero tells us, he died in the midst of his intellectual labors ("scribens est mortuus") ("De Senect.", v, 13).

II. WORKS

It is practically certain that all Plato's genuine works have come down to us. The lost works ascribed to him, such as the "Divisions" and the "Unwritten Doctrines", are certainly not genuine. Of the thirty-six dialogues, some — the "Phaedrus", "Protagoras", "Phaedo", "The Republic", "The Banquet", etc. — are undoubtedly genuine; others — e.g. the "Minos", — may with equal certainty be considered spurious; while still a third group — the "Ion", "Greater Hippias", and "First Alcibiades" — is of doubtful authenticity. In all his writings, Plato uses the dialogue with a skill never since equalled. That form permitted him to develop the Socratic method of question and answer. For, while Plato elaborated to a high degree the faculty by which the abstract is understood and presented, he was Greek enough to follow the artistic instinct in teaching by means of a clear-cut concrete type of philosophical excellence. The use of the myth in the dialogues has occasioned considerable difficulty to the commentators and critics. When we try to put a value on the content of a Platonic myth, we are often baffled by the suspicion that it is all meant to be subtly ironical, or that it is introduced to cover up the inherent contradictions of Plato's thought. In any case, the myth should never be taken too seriously or invoked as an evidence of what Plato really believed.

III. PHILOSOPHY

(1) The Starting Point

The immediate starting-point of Plato's philosophical speculation was the Socratic teaching. In his attempt to define the conditions of knowledge so as to refute sophistic scepticism, Socrates had taught that the only true knowledge is a knowledge by means of concepts. The concept, he said, represents all the reality of a thing. As used by Socrates, this was merely a principle of knowledge. It was taken up by Plato as a principle of Being. If the concept represents all the reality of things, the reality must be something in the ideal order, not necessarily in the things themselves, but rather above them, in a world by itself. For the concept, therefore, Plato substitutes the Idea. He completes the work of Socrates by teaching that the objectively real Ideas are the foundation and justification of scientific knowledge. At the same time he has in mind a problem which claimed much attention from pre-Socratic thinkers, the problem of change. The Eleatics, following Parmenides, held that there is no real change or multiplicity in the world, that reality is one. Heraclitus, on the contrary, regarding motion and multiplicity as real, maintained that permanence is only apparent. The Platonic theory of Ideas is an attempt to solve this crucial question by a metaphysical compromise. The Eleatics, Plato said, are right in maintaining that reality does not change; for the ideas are immutable. Still, there is, as Heraclitus contended, change in the world of our experience, or, as Plato terms it, the world of phenomena. Plato, then, supposes a world of Ideas apart from the world of our experience, and immeasurably superior to it. He imagines that all human souls dwelt at one time in that higher world. When, therefore, we behold in the shadow-world around us a phenomenon or appearance of anything, the mind is moved to a remembrance of the Idea (of that same phenomenal thing) which it formerly contemplated. In its delight it wonders at the contrast, and by wonder is led to recall as perfectly as possible the intuition it enjoyed in a previous existence. This is the task of philosophy. Philosophy, therefore, consists in the effort to rise from the knowledge of phenomena, or appearances, to the noumena, or realities. Of all the ideas, however, the Idea of the beautiful shines out through the phenomenal veil more clearly than any other; hence the beginning of all philosophical activity is the love and admiration of the Beautiful.

(2) Division of Philosophy

The different parts of philosophy are not distinguished by Plato with the same formal precision found in Aristotelean, and post-Aristotelean systems. We may, however, for convenience, distinguish:

Dialectic, the science of the Idea in itself;

Physics, the knowledge of the Idea as incorporated or incarnated in the world of phenomena, and

Ethics and Theory of the State, or the science of the Idea embodied in human conduct and human society.

(a) Dialectic

This is to be understood as synonymous not with logic but with metaphysics. It signifies the science of the Idea, the science of reality, science in the only true sense of the word. For the ideas are the only realities in the world. We observe, for instance, just actions, and we know that some men are just. But both in the actions and in the persons designated as just there exist many imperfections; they are only partly just. In the world above us there exits justice, absolute, perfect, unmixed with injustice, eternal, unchangeable, immortal. This is the Idea of justice. Similarly, in that world above us there exist the Ideas of greatness, goodness, beauty, wisdom, etc. and not only these, but also the Ideas of concrete material objects such as the Idea of man, the idea of horse, the Idea of trees, etc. In a word, the world of Ideas is a counterpart of the world of our experience, or rather, the latter is a feeble imitation of the former. The ideas are the prototypes, the phenomena are ectypes. In the allegory of the cave (Republic, VII, 514 d) a race of men are described as chained in a fixed position in a cavern, able to look only at the wall in front of them. When an animal, e.g. a horse, passes in front of the cave, they, beholding the shadow on the wall, imagine it to be a reality, and while in prison they know of no other reality. When they are released and go into the light they are dazzled, but when they succeed in distinguishing a horse among the objects around them, their first impulse is to take that for a shadow of the being which they saw on the wall. The prisoners are "like ourselves", says Plato. The world of our experience, which we take to be real, is only a shadow world. The real world is the world of Ideas, which we reach, not by sense-knowledge, but by intuitive contemplation. The Ideas are participated by the phenomena; but how this participation takes place, and in what sense the phenomena are imitations of the Ideas, Plato does not fully explain; at most he invokes a negative principle, sometimes called "Platonic Matter", to account for the falling-off of the phenomena from the perfection of the Idea. The limitating principle is the cause of all defects, decay, and change in the world around us. The just man, for instance, falls short of absolute justice (the Idea of Justice), because in men the Idea of justice is fragmented, debased, and reduced by the principle of limiation. Towards the end of his life, Plato leaned more and more towards the Pythagorean number-theory, and, in the "Timaeus" especially, he is inclined to interpret the Ideas in terms of mathematics. His followers emphasized this element unduly, and, in the course of neo-Platonic speculation, the ideas were identified with numbers. There was much in the theory of Ideas that appealed to the first Christian philosophers. The emphatic affirmation of a supermundane, spiritual order of reality and the equally emphatic assertion of the caducity of things material fitted in with the essentially Christian contention that spiritual interests are supreme. To render the world of Ideas more acceptable to Christians, the Patristic Platonists from Justin Martyr to St. Augustine maintained that the world exists in the mind of God, and that this was what Plato meant. On the other hand, Aristotle understood Plato to refer to a world of Ideas self-subsisting and separate. Instead, therefore, of picturing to ourselves the world of Ideas as existing in God, we should represent God as existing in the world of Ideas. For, among the Ideas, the hierarchical supremacy is attributed to the Idea of God, or absolute Goodness, which is said to be for the supercelestial universe what the sun in the heavens is for this terrestrial world of ours.

(b) Physics

The Idea, incorporated, so to speak, in the phenomenon is less real than the Idea in its own world, or than the Idea embodied in human conduct and human society. Physics, i.e., the knowledge of the Idea in phenomena, is, therefore, inferior in dignity and importance to Dialectic and Ethics. In fact, the world of phenomena has no scientific interest for Plato. The knowledge of it is not true knowledge, nor the source, but only the occasion of true knowledge. The phenomena stimulate our minds to a recollection of the intuition of Ideas, and with that intuition scientific knowledge begins. Moreover, Plato's interest in nature is dominated by a teleological view of the world as animated with a World-Soul, which, conscious of its process, does all things for a useful purpose, or, rather, for "the best", morally, intellectually, and aesthetically. This conviction is apparent especially in the Platonic account of the origin of the universe, contained in the "Timaeus", although the details regarding the activity of the demiurgos and the created gods should not, perhaps, be taken seriously. Similarly, the account of the origin of the soul, in the same dialogue, is a combination of philosophy and myth, in which it is not easy to distinguish the one from the other. It is clear, however, that Plato holds the spiritual nature of the soul as against the materialistic Atomists, and that he believes the soul to have existed before its union with the body. The whole theory of Ideas, in so far, at least, as it is applied to human knowledge, presupposes the doctrine of pre-existence. "All knowledge is recollection" has no meaning except in the hypothesis of the soul's pre-natal intuition of Ideas. it is equally incontrovertible that Plato held the soul to be immortal. His conviction on this point was as unshaken as Socrates's. His attempt to ground that conviction on unassailable premises is, indeed, open to criticism, because his arguments rest either on the hypothesis of previous existence or on his general theory of Ideas. Nevertheless, the considerations which he offers in favour of immortality, in the "Phaedo", have helped to strengthen all subsequent generations in the belief in a future life. His description of the future state of the soul is dominated by the Pythagorean doctrine of transmigration. Here, again, the details are not to be taken as seriously as the main fact, and we can well imagine that the account of the soul condemned to return in the body of a fox or a wolf is introduced chiefly because it accentuates the doctrine of rewards and punishments, which is part of Plato's ethical system. Before passing to his ethical doctrines it is necessary to indicate one other point of his psychology. The soul, Plato teaches, consists of three parts: the rational soul, which resides in the head; the irascible soul, the seat of courage, which resides in the heart; and the appetitive soul, the seat of desire, which resides in the abdomen. These are not three faculties of one soul, but three parts really distinct.

(c) Ethics and Theory of the State

Like all the Greeks, Plato took for granted that the highest good of man, subjectively considered, is happiness (eudaimonia). Objectively, the highest good of man is the absolutely highest good in general, Goodness itself, or God. The means by which this highest good is to be attained is the practice of virtue and the acquistion of wisdom. So far as the body hinders these pursuits it should be brought into subjection. Here, however, asceticism should be moderated in the interests of harmony and symmetry — Plato never went the length of condemning matter and the human body in particular, as the source of all evil — for wealth, health, art, and innocent pleasures are means of attaining happiness, though not indispensable, as virtue is. Virtue is order, harmony, the health of the soul; vice is disorder, discord, disease. The State is, for Plato, the highest embodiment of the Idea. It should have for its aim the establishment and cultivation of virtue. The reason of this is that man, even in the savage condition, could, indeed, attain virtue. In order, however, that virtue may be established systematically and cease to be a matter of chance or haphazard, education is necessary, and without a social organization education is impossible. In his "Republic" he sketches an ideal state, a polity which should exist if rulers and subjects would devote themselves, as they ought, to the cultivation of wisdom. The ideal state is modelled on the individual soul. It consists of three orders: rulers (corresponding to the reasonable soul), producers (corresponding to desire), and warriors (corresponding to courage). The characteristic virtue of the producers is thrift, that of the soldiers bravery, and that of the rulers wisdom. Since philosophy is the love of wisdom, it is to be the dominant power in the state: "Unless philosophers become rulers or rulers become true and thorough students of philosophy, there shall be no end to the troubles of states and of humanity" (Rep., V, 473), which is only another way of saying that those who govern should be distinguished by qualities which are distinctly intellectual. Plato is an advocate of State absolutism, such as existed in his time in Sparta. The State, he maintains, exercises unlimited power. Neither private property nor family institutions have any place in the Platonic state. The children belong to the state as soon as they are born, and should be taken in charge by the State from the beginning, for the purpose of education. They should be educated by officials appointed by the State, and, according to the measure of ability, which they exhibit, they are to be assigned by the State to the order of producers, to that of warriors, or to the governing class. These impractical schemes reflect at once Plato's discontent with the demagogy then prevalent in Athens and in his personal predilection for the aristocratic form of government. Indeed, his scheme is essentially aristocratic in the original meaning of the word; it advocates government by the (intellectually) best. The unreality of it all, and the remoteness of its chance to be tested by practice, must have been evident to Plato himself. For in his "Laws" he sketches a modified scheme which, though inferior, he thinks, to the plan outlined in the "Republic", is nearer to the level of what the average state can attain.

IV. THE PLATONIC SCHOOL

Plato's School, like Aristotle's, was organized by Plato himself and handed over at the time of his death to his nephew Speusippus, the first scholarch, or ruler of the school. It was then known as the Academy, because it met in the groves of Academus. The Academy continued, with varying fortunes, to maintain its identity as a Platonic school, first at Athens, and later at Alexandria until the first century of the Christian era. It modified the Platonic system in the direction of mysticism and demonology, and underwent at least one period of scepticism. It ended in a loosely constructed eclecticism. With the advent of neo-Platonism (q.v.) founded by Ammonius and developed by Plotinus, Platonism definitely entered the cause of Paganism against Christianity. Nevertheless, the great majority of the Christian philosophers down to St. Augustine were Platonists. They appreciated the uplifting influence of Plato's psychology and metaphysics, and recognized in that influence a powerful ally of Christianity in the warfare against materialism and naturalism. These Christian Platonists underestimated Aristotle, whom they generally referred to as an "acute" logician whose philosophy favoured the heretical opponents of orthodox Christianity. The Middle Ages completely reversed this verdict. The first scholastics knew only the logical treatises of Aristotle, and, so far as they were psychologists or metaphysicians at all, they drew on the Platonism of St. Augustine. Their successors, however, in the twelfth century came to a knowledge of the psychology, metaphysics, and ethics of Aristotle, and adopted the Aristotelean view so completely that before the end of the thirteenth century the Stagyrite occupied in the Christian schools the position occupied in the fifth century by the founder of the Academy. There were, however, episodes, so to speak, of Platonism in the history of Scholasticism — e.g., the School of Chartes in the twelfth century — and throughout the whole scholastic period some principles of Platonism, and especially of neo-Platonism, were incorporated in the Aristotelean system adopted by the schoolmen. The Renaissance brought a revival of Platonism, due to the influence of men like Bessarion, Plethon, Ficino, and the two Mirandolas. The Cambridge Platonists of the seventeenth century, such as Cudworth, Henry More, Cumberland, and Glanville, reacting against humanistic naturalism, "spiritualized Puritanism" by restoring the foundations of conduct to principles intuitionally known and independent of self-interest. outside the schools of philosophy which are described as Platonic there are many philosophers and groups of philosophers in modern times who owe much to the inspiration of Plato, and to the enthusiasm for the higher pursuits of the mind which they derived from the study of his works.